1. Field of the Invention
The invention relates to methods and assemblies for controlling the impingement of solar radiation on building structures and more particularly relates to methods and apparatus for the reduction of heat gain by concrete structures exposed to direct solar radiation.
2. Brief Description of the Prior Art
Concrete building structures are found throughout the world. They have found particular favor in tropical and semitropical zones because of their resistance to rot, corrosion and deformation under relatively humid conditions. However, concrete structures are not without their own particular problems of maintenance and use. For example, concrete structures are ideal heat sinks, with the ability to absorb about 230 BTU per hour from solar radiation. If the concrete is dark in color, absorption of solar radiation is further enhanced. In humid climates, concrete is a substrate which favors the growth of certain bacteria and molds which are dark in color. As these bacteria and molds proliferate, the affect is a darkening of the concrete surface so that absorption of solar radiation is further favored over a period of time.
Concrete is also a conductor of thermal energy and will freely radiate absorbed thermal energy. Thus, during exposure to the sun, concrete absorbs thermal energy in large quantities. When the day is ended, the concrete radiates the absorbed energy to the surrounding environment. As one practical example of the affect of this absorption/radiation cycle one might cite the situation found in Puerto Rico where many residences are concrete structures. During the daylight hours, exposed concrete, acting as a heat-sink, may absorb thermal energy from solar radiation to the extent that the concrete reaches temperatures of from 130.degree. F. to 150.degree. F. This thermal energy is transmitted to both inner and outer wall surfaces of the concrete structure and radiated to both the inside and outside of the building. After the sun has set in the sky, radiation will continue through the night. Often the temperatures inside the building will be uncomfortable for residents until the early morning hours, unless air conditioning is employed.
Also, in Puerto Rico and like areas with similar climates, rainfall is experienced on a daily or near daily basis. As these cool rains strike hot concrete, the resulting cooling effect is so sudden that the concrete may crack under the stress of thermal shock. This of course requires additional maintenance activity if the building is to be maintained properly.
By the method of my invention, employing the assembly of the invention, the above-described problems may be resolved. Concrete structures, particularly roofs exposed to direct sunlight are shielded and protected from solar radiation with its consequences. The assembly of the invention may be considered a passive type of cooling system for concrete structures that require little maintenance, having no moving parts, valves etc. and no power (energy) requirements for operation. The assembly is simple to construct.